1. Field of the Invention
The present invention relates to an image reading device that has a blank-paper detection unit for detecting a blank-paper original, and to an image forming apparatus equipped with the image reading device.
2. Description of the Related Art
There is a known image reading device equipped with a moving image reading means that reads originals while feeding originals stacked on an original tray one by one by an automatic document feeder (hereinafter referred to as an “ADF”). In such an image reading device, when an original passes over a read glass of an image reading section, an original is irradiated with a light from a light source and a reflected light from the original is reflected by mirrors so that the light enters an image pickup device, such as a CCD, to read an image through an image formation lens.
However, if a user erroneously mixes a blank-paper original on which no image is formed into a bundle of originals when copying a plurality of originals continuously, a blank sheet that is not needed to print essentially is output as a result of a copy of the blank-paper original. In this case, there is a problem that a paper resource is consumed vainly. Similarly, when reading results of originals are saved as an image file, and when an image of a blank-paper original that is not needed to save essentially is saved erroneously, file capacity becomes larger than needed. Then, since data of a blank page that a user does not intend is mixed in a file, the data that is not desirable for a user is saved.
In order to solve such a problem, there is a known technique that provides a blank-paper detection means so that image data of an original determined as a blank-paper original without printing information is not copied or is not saved as a file, and that excepts a blank-paper original from an image processing target.
Incidentally, the blank-paper detection means determines whether an original is blank paper by determining whether printing information is included in an image area. And accordingly, the blank-paper detection means needs to change a setting about an image area within which blank-paper detection is performed (hereinafter referred to as a “blank-paper detection area”) according to a size of an original (hereinafter referred to as an “original size”). For example, when the blank-paper detection area is set outside an original (i.e., is set as an area wider than an actual original), garbage adhered outside the original may be detected as printing information, which causes erroneous detection that a blank-paper original is not detected as a blank-paper original. On the other hand, when the blank-paper detection area is set inside an original (i.e., is set as an area narrower than an actual original), an original including useful printing information in its peripheral area may be erroneously detected as a blank-paper original. When the useful printing information, such as a page number or a ruled line, is printed in an original, a user wants not to determine that the original is a blank-paper original, in general. Thus, the image reading device that has the blank-paper detection means is required to set the blank-paper detection area correctly according to an original size.
There is a suggested image processing apparatus that is provided with a first determination function for performing blank-paper detection in the entire reading area, and a second determination function for performing blank-paper detection in an effective image area that is formed by cutting off an edge of the reading area (see Japanese Laid-Open Patent Publication (Kokai) No. 2006-279094 (JP 2006-279094A)). In this image processing apparatus, even in a case where the first determination function determines that an original is not blank paper, when the second determination function determines that the original is blank paper, the result of the second determination function takes priority, and it is determined that the original is blank paper. This image processing apparatus seems to enable a correct blank-paper determination because the blank-paper determination is executed by excepting an area in which an erroneous determination may occur.
Moreover, there is a suggested technique that displays a blank-paper detection area on a screen of an operation unit of an image reading device so that a user can change a setting about the blank-paper detection area as needed (see Japanese Laid-Open Patent Publication (Kokai) No. 2012-80231 (JP 2012-80231A)).
However, the technique of JP 2006-279094A is difficult to set the blank-paper detection area correctly when a user copies, at a time, an original bundle in which originals of a regular size and originals of an irregular size are mixed. For example, even if the blank-paper detection area of an original of an irregular size is set as the same as the blank-paper detection area of an original of the nearest regular size, there is a possibility that the blank-paper detection area includes an area outside the original or that the image area is cut off and necessary printing information is overlooked. Moreover, even when a user designates a regular size on the operation screen, an original size to be actually copied may different from the designated size. Particularly, a blank-paper detection area of an original of an irregular size cannot be set correctly even when a user designates the blank-paper detection area of the original as the same as the blank-paper detection area of an original of the nearest regular size.
On the other hand, since the technique of JP 2012-80231A needs to check whether the blank-paper detection area is set correctly while looking the setting result on the operation screen one by one or needs to change the setting of the blank-paper detection area, the operation is complicated for a user. Moreover, in the case of where different width originals are mixed and loaded on a tray in order to copy the originals at a time, since a blank-paper detection area cannot be determined uniquely, a user needs to adjust a blank-paper detection area for every sheet, which takes time too much and is poor in practicality.
In this way, an image reading device that has a blank-paper detection means has a problem in that a setting of a blank-paper detection area is not easy and that erroneous determination in blank-paper detection easily occurs due to erroneous setting of blank-paper detection area. In particular, an original of an irregular size has high possibility of causing erroneous determination in blank-paper detection.